Low Impact Development (LID) Siting Methodology: A Guide to Siting LID Projects Using A GIS and AHP

The purpose of this research project is to develop a straightforward and cost-effective methodology that skilled geographic information system (GIS) users within local governments and nonprofit organizations can use to identify sites that have the greatest potential for Limited Impact Design (LID) stormwater management projects. The methodology is applied to watersheds in Western Contra Costa County, California. A review of LID manuals guided the selection of site suitability criteria and professional opinions from two stormwater managers guided the ranking of the criteria. The Analytical Hierarchy Process (AHP) was used to convert these rankings into coefficients which were then applied to the chosen criteria. A GIS was used to develop site suitability rankings of the study area. Maps depicting suitable sites for LID placement were generated using this methodology. These maps act as a guide that the aforementioned groups can use for LID project planning. The top ranked sites, suitable for LID, identified by the methodology were primarily areas with large parking lots and building footprints. These sites should be targeted for LID projects because they are often the largest contributors to hydrograph modification and have most significantly altered the site hydrology.